1. Field of the Invention
The present invention relates to an IC (Integrated Circuit) card reader/writer and, more particularly, to an IC card reader/writer for use with a business transactions processing apparatus which is operable with an IC card for executing various kinds of business transactions.
2. Description of the Prior Art
In parallel with the extensive use of IC cards, a card transactions processing apparatus capable of processing various kinds of business transactions data by using an IC card is attracting much attention and has been put to practical use. In general, a card transactions processing apparatus may be implemented by a keyboard, a display, a printer, an IC card reader/writer, and a pin pad.
When the processing apparatus having the above construction is loaded with an IC card, the IC card reader/writer reads data which are stored in the IC card. As one manipulates the keyboard to enter a transaction command and a key, a particular operation procedure or guidance is indicated on the display. When the operator sequentially enters data on the keyboard according to the guidance appearing on the display, the data are transmitted to central equipment to be processed thereby. The result of processing returned from the central equipment may be printed out by the printer of the processing apparatus, as needed.
Generally, an IC card has a particular operating clock frequency which is selected before it is issued. The predominant frequency mode selected for IC cards is, for example, 4.9152 megahertz mode in Japan and 3.579545 megahertz mode in U.S.A. and France. A prior art IC card reader/writer, therefore, has a clock generator implemented by an oscillator exclusively oscillating clock pulses having a frequency of 4.9152 megahertz or an oscillator exclusively oscillating clock pulses whose frequency is 3.579545 megahertz.
The single-frequency clock generator scheme stated above is undesirable from the standpoint of applicable range. Specifically, when an IC card reader/writer whose clock generator oscillates at a certain fixed clock frequency is loaded with an IC card which is operable in a different frequency mode, the reader/writer cannot read data out of the IC card at all so that the processing apparatus is practically useless.